A solid state drive (SSD) is a data storage device using integrated circuit assemblies as memory to store data persistently. SSDs have no moving mechanical components, which distinguish them from traditional electromechanical magnetic disks such as hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read/write heads. Compared with electromechanical disks, SSDs are typically less susceptible to physical shock, run more quietly, have lower access time, and less latency. In addition, most SSDs use NAND-based flash memory, which retains data without power. However, since NAND-flash memory has a finite limit of program-erase cycles, monitoring and managing the wear is critical to reliability of the drive.
SSDs have performance advantages in random workloads when compared to HDDs. In a tiered storage system, such as a RAID (redundant array of independent disks) array, the basic use case is to move random workloads to an SSD array. However, random workloads result in more parity updates in a RAID array, so the SSDs will have more write operations. More write operations result in the SSD reaching its write limit faster, increasing the likelihood the drive will fail.